The discrepancies between single-blind and double-blind methods in animal pharmacological research are noteworthy and should be better investigated, also in non-homeopathic research.

1. BioMed Central
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BMC Complementary and
Alternative Medicine
Open AccessResearch article
Rat models of acute inflammation: a randomized controlled study
on the effects of homeopathic remedies
Anita Conforti1, Paolo Bellavite2, Simone Bertani1, Flavia Chiarotti*3,
Francesca Menniti-Ippolito4 and Roberto Raschetti4
Address: 1Department of Medicine-Public Health, University of Verona, Policlinico G.B. Rossi, Piazzale L.A. Scuro, 33100 Verona, Italy,
2Department of Morphological-Biomedical Sciences, University of Verona, Policlinico G.B. Rossi, Piazzale L.A. Scuro, 33100 Verona, Italy,
3Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy and 4National Centre for
Epidemiology, Surveillance and Health Promotion, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
Email: Anita Conforti - aconforti@sfm.univr.it; Paolo Bellavite - paolo.bellavite@univr.it; Simone Bertani - simone.2.bertani@gsk.com;
Flavia Chiarotti* - flavia.chiarotti@iss.it; Francesca Menniti-Ippolito - francesca.menniti@iss.it; Roberto Raschetti - roberto.raschetti@iss.it
* Corresponding author
Abstract
Background: One of the cardinal principles of homeopathy is the "law of similarities", according to which patients can be
treated by administering substances which, when tested in healthy subjects, cause symptoms that are similar to those
presented by the patients themselves. Over the last few years, there has been an increase in the number of pre-clinical (in
vitro and animal) studies aimed at evaluating the pharmacological activity or efficacy of some homeopathic remedies under
potentially reproducible conditions. However, in addition to some contradictory results, these studies have also highlighted
a series of methodological difficulties.
The present study was designed to explore the possibility to test in a controlled way the effects of homeopathic remedies
on two known experimental models of acute inflammation in the rat. To this aim, the study considered six different
remedies indicated by homeopathic practice for this type of symptom in two experimental edema models (carrageenan-
and autologous blood-induced edema), using two treatment administration routes (sub-plantar injection and oral
administration).
Methods: In a first phase, the different remedies were tested in the four experimental conditions, following a single-blind
(measurement) procedure. In a second phase, some of the remedies (in the same and in different dilutions) were tested by
oral administration in the carrageenan-induced edema, under double-blind (treatment administration and measurement)
and fully randomized conditions. Seven-hundred-twenty male Sprague Dawley rats weighing 170–180 g were used. Six
homeopathic remedies (Arnica montana D4, Apis mellifica D4, D30, Atropa belladonna D4, Hamamelis virginiana D4, Lachesis
D6, D30, Phosphorus D6, D30), saline and indomethacin were tested. Edema was measured using a water-based
plethysmometer, before and at different times after edema induction. Data were analyzed by ANOVA and Student t test.
Results: In the first phase of experiments, some statistically significant effects of homeopathic remedies (Apis, Lachesis and
Phosporus) were observed (the reduction in paw volume increase ranging from 10% to 28% at different times since edema
induction). In the second phase of experiments, the effects of homeopathic remedies were not confirmed. On the contrary,
the unblinded standard allopathic drug indomethacin exhibited its anti-inflammatory effect in both experimental phases (the
reduction in paw volume increase ranging from 14% to 40% in the first phase, and from 18% to 38% in the second phase
of experiments).
Conclusion: The discrepancies between single-blind and double-blind methods in animal pharmacological research are
noteworthy and should be better investigated, also in non-homeopathic research.
Published: 17 January 2007
BMC Complementary and Alternative Medicine 2007, 7:1 doi:10.1186/1472-6882-7-1
Received: 01 August 2006
Accepted: 17 January 2007
This article is available from: http://www.biomedcentral.com/1472-6882/7/1
© 2007 Conforti et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Background
One of the cardinal principles of homeopathic theory of
medicine is the "law of similarities", according to which
patients can be treated by administering substances
which, when tested in healthy subjects, cause symptoms
that are similar to those presented by the patients them-
selves. Another important principle is that of "minimal
dilution": to use the lowest concentration of a substance
that still provokes a response [1].
Over the last few years, there has been an increase in the
number of pre-clinical (in vitro and animal) studies aimed
at evaluating the pharmacological activity or efficacy of
some homeopathic remedies under potentially reproduc-
ible conditions. Among them, animal studies have shown
that a homeopathic complex containing low dilutions/
dynamizations of Arnica montana, Atropa belladonna,
Hamamelis virginiana and other compounds has a slight
but significant effect on experimental rat paw inflamma-
tion caused by the injection of autologous blood [2] and
during the acute phase of arthritis induced in rat by means
of the injection of heat-killed Mycobacterium butyricum [3].
Moreover, Apis mellifica is a hydro-alcoholic extract of the
body of bee that, according to the law of similarities and
data derived by homeopathic literature, could have anti-
inflammatory or anti-edemagenic activity [4-8]. Lachesis,
the venom of the Crotalus mutus snake, and Phosphorus are
remedies indicated in the homeopathic literature for dis-
eases with hemorrhagic tendencies, but no controlled
investigations have been published so far. High dilutions/
dynamizations of Atropa belladonna [9] and Phosphorus
[10] have been found to have a slight in vitro inhibitory
effect on neutrophil granulocytes, which play a funda-
mental role in acute inflammation. However, in addition
to some contradictory results, the pre-clinical studies have
also highlighted a series of methodological difficulties,
related to the very low concentration and activity of the
medicines (requiring higher number of experimental ani-
mals) and to the largely unknown factors affecting their
stability in time or their pharmacokinetics [11]. On the
other hand, small clinical studies, carried out under
selected conditions on Arnica montana, Atropa belladonna
and Hamamelis virginiana, have found that, alone or in
combination, they could have some anti-inflammatory
activity [12-17].
Therefore, the objective of our study was to evaluate,
through an animal-based model, the efficacy of the above-
mentioned remedies, which are usually prescribed by
homeopathists to treat clinical conditions characterized
by inflammatory or hemorrhagic manifestations.
The study was organized in two distinct randomized
experimental controlled phases.
Experiment A was planned to study the largest possible
number of conditions (homeopathic remedies, adminis-
tration routes and edema models) compatible with the
technical requirements and reasonable costs of the tests.
Subsequently, a selection of the above-mentioned condi-
tions was re-tested (experiment B) with special attention
to confounding factors, which could interfere with the
assessment of treatments. Specifically, we re-tested those
homeopathic remedies, edema model and administration
route which in Experiment A gave paw volume increases
significantly lower than physiological solution, at most
times since edema induction.
This study was conducted within a National Project on
Unconventional Therapies coordinated by the Italian
National Institute of Health (Istituto Superiore di Sanità,
Rome, Italy) and funded by the Italian Ministry of Health.
Methods
The general scheme of the study is shown in Table 1. On
the overall, 40 different experimental treatment groups
were studied, namely 32 groups in Experiment A (2
edema models × 2 administration routes × 8 treatments)
and 8 groups in Experiment B (1 edema model × 1 admin-
istration route × 8 treatments).
Study setting
All the experimental activities were carried out at the
Departments of Medicine-Public Health and of Morpho-
logical-Biomedical Sciences, University of Verona. Data
analysis was performed at the Istituto Superiore di Sanità
in Rome.
Animals
Male Sprague Dawley rats (Harlan Italy) weighing 170–
180 g were used for both experiments A and B. Rats were
housed for six days from arrival to testing, and their indi-
vidual weight was collected at arrival and at the day of test-
ing. Increase in rat weight was used as a measure of animal
well being. During the course of all replications (experi-
ments A and B), the animals were kept in a room other
than that used for the treatments and measurements.
The study was conducted in conformity with the Italian
regulations governing the protection of laboratory ani-
mals used for experimental purposes (permission granted
by Ministry of Health, according to Law Decree No. 116/
92). At the end of each experiment, the animals were sac-
rificed by means of ether anesthesia.
Remedies
We chose to use the homeopathic remedies Arnica mon-
tana, Atropa belladonna, Apis mellifica, Hamamelis virgin-
iana, Lachesis, and Phosphorus at the lowest marketed
dilutions/dynamizations (from D4 to D6, depending on

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the remedy). This choice was based on the hypothesis fre-
quently sustained in the homeopathic literature that the
treatment of local symptoms and acute cell or organic
reactions requires lower doses than the treatment of gen-
eral symptoms and chronic diseases. The D30 dilution
was added in the second phase of experiments, to com-
pare possible dose-related differences in treatment effects.
Furthermore, we chose to use the preparations available
in physiological solution because this allowed us to
administer the same formulation orally and by injection.
The two ways of administration were initially chosen
because this experiment was designed to explore and
screen the widest possible range of methodological varia-
bles, in order to maximize the possibility of pointing out
significant effects, if present. The homeopathic remedies
(1 ml glass vials containing a sterile isotonic solution)
were produced in accordance with the German homeo-
pathic pharmacopoeia (HAB) [18]. Sterilization was done
by dry heat sterilization, ionizing radiation, or filtration
according to the different substances of the mother tinc-
ture, as described in HAB (Arnica rule n. 4a, Atropa bella-
donna rule n. 2a, Hamamelis rule 3a, Apis mellifica rule
4b, Lachesis e Phosphorus follow specific rules). Dilution
and dynamization (succussion) was done in glass vials
under sterile conditions.
A sterile saline physiological solution (0.9% NaCl) was
used as reference inert treatment (placebo). Indomethacin
(Sigma) was dissolved in sterile water for injections at a
concentration of 10 mg/ml immediately before the tests.
Indomethacin was administered intramuscularly as active
reference treatment (standard non-steroidal anti-inflam-
Table 1: General scheme of the study
Phase A Phase B
Randomisation
by cages
within cages by treatments -
Blinding
Treatment administration -
Edema measurement
Inflammation model CA BL CA
Homeopathic remedies
dilution n. of animals studied
Arnica D4 71 O/I O/I -
Apis D4 90 O/I O/I O
Apis D30 18 - - O
Atropa D4 72 O/I O/I -
Hamamelis D4 72 O/I O/I -
Lachesis D6 86 O/I O/I O
Lachesis D30 18 - - O
Phosphorus D6 90 O/I O/I O
Phosphorus D30 18 - - O
Reference treatments
Placebo:
Physiological solution 86 O/I O/I O
Active comparator:
Indomethacin 88 I/I I/I I
O = oral administration
I = administration through injection
CA = carrageenan induced edema
BL = autologous blood induced edema
Each treatment group has been tested through 3 replications. In each replication 6 rats were studied. In experiment A 11 rats were excluded from
the analyses because of problems with edema induction.

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matory drug), to check the suitability of the model in
revealing a potential drug effect, if present. Therefore, we
were not interested in comparing quantitatively its effect
with those of homeopathic medicines.
Animal models
We used two different rat models of acute inflammation,
in order to explore the effect of a series of treatments in
conditions which differed, at least in part, in their patho-
physiological mechanisms. Specifically, the first model is
based on the use of a classical irritating, edema-causing,
substance (carrageenan-induced edema), and involves the
activation of the arachidonic acid cascade, giving rise to
the formation of the principal mediators of inflammation
(prostaglandins and thromboxanes). This model is com-
monly used to screen conventional non-steroidal anti-
inflammatory drug [19]. The second one (used only in
experiment A) is the autologous blood-induced edema
model recently developed by the Verona group, which
mimics a traumatic condition involving the perfusion of
blood into the joint (typical of common sprains and
bruises) and the development of inflammation lasting a
few hours. We already used it to study the regulating
power of a homeopathic complex [2].
Edema induction
The edema was induced by injecting 0.1 ml of carrageenan
0.5% in physiological solution or 0.1 ml of autologous
blood into the sole of the right posterior paw. The carra-
geenan (Sigma) was dissolved the day before the experi-
ment, homogenized in a potter and stored in the dark at
+4°C. Preliminary studies have shown that this dose of
carrageenan induces a medium-large edema in compari-
son with a maximum dose. Immediately before the exper-
iment, the solution was re-homogenized. The autologous
blood was drawn from two ether-anesthetized syngenic
rats by means of a cardiac puncture, and made uncoagula-
ble by the addition of heparin.
Treatments
The homeopathic remedies were administered immedi-
ately after edema induction. The oral treatment was per-
formed using an insulin syringe without a needle spraying
0.1 ml of the remedy or of the physiological solution
(control group) into the oral cavity above the tongue, and
then immediately returning the animal to its cage. The
injection treatment was performed injecting 0.1 ml of the
remedy or of physiological solution into underside of the
right posterior paw using an insulin syringe. Indometh-
acin (standard treatment) was injected intramuscularly
(0.1 ml/hg) 30 minutes before edema induction in order
to allow its absorption. In the sub plantar experiments,
the group of rats treated with indomethacin was also
given a sub plantar injection of 0.1 ml of sterile physiolog-
ical solution at the time of edema induction. In this way,
the initial increase in paw volume due only to the sub
plantar injections (a total of 0.2 ml) was the same as that
in the rats treated with the homeopathic remedies.
Treatment assignment
At arrival, animals were taken from transport cages one-
by-one and sequentially transferred to the homecages. In
Experiment A the subsequent couples of animals were
located in different cages, until six animals were housed in
the same cage. The whole cage was then assigned to one of
the different treatments, according to an assignment list
different from replication to replication. On the contrary,
in Experiment B eight animals consecutively taken from
transport cages were housed in the same homecage, and
then assigned to treatments (one animal per treatment)
according to an assignment list different among cages and
replications.
Blinding procedures
Experiment A. Homeopathic remedies were sucked up by
a syringe directly from the purchased glass vials just before
administration to animals. All cagemates received the
same treatment, which differed from cage to cage. Cages
were attributed different codes, and animals within cages
were individually marked with a permanent staining on
different parts of the body. The person charged with paw
volume measurements was the only one that was blind to
treatments among those working on animals (single
blind). He used cage and animal codes to recognize indi-
viduals and to report repeated measurements on data col-
lection forms. Experiment B. The homeopathic remedies
and the sterile physiological solution of 0.9% NaCl were
transferred (1 ml) in 1.5 ml sterile plastic vials with caps
and labeled at the Department of Morphological-Biomed-
ical Sciences, University of Verona. These vials were then
sent to Istituto Superiore di Sanità (ISS), Rome, in a single
package box divided in several compartments, where each
vial was separated from the others by a cardboard wall. At
ISS, a person not involved in the experimental trial coded
them with a letter, and sent them back to the experimental
laboratory (Verona), where they were used within 1
month. Animals were housed in 6 cages (8 rats in each
cage) and individually marked with a permanent staining
on different parts of the body. Each cagemate received a
different coded treatment. The correspondence between
code and remedies was notified only at the end of the
experiments and after the statistical analyses were com-
pleted. Therefore, treatment administration and paw vol-
ume measurement were performed by persons both blind
to treatments (double-blind). Blinding was not applied to
indomethacin treatment.
After coding of treatments, a qualitative analysis was per-
formed through ultraviolet (UV) absorption spectra on
samples of homeopathic treatments, saline and

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indomethacin. UV analysis performed on homeopathic
and saline samples showed the absence of the characteris-
tic absorption band of indomethacin (maximum at 318
nm, according to the European Pharmacopoeia).
Measurements of the edema
The paw volume was measured, in both experiments A
and B, using a water-based plethysmometer (U. Basile,
Milan) before edema induction (time 0) and after 1, 3, 5
and 7 hours (carrageenan-induced edema) or 1, 2, 3 and
5 hours (blood-induced edema). The change in paw vol-
ume due to the carrageenan or blood injection, edema
and eventually remedy (in the case of sub plantar route of
administration), was computed for each rat as difference
between paw volume at each time from edema induction
(1 hr, 2 hr, 3 hr, 5 hr, 7 hr) and paw volume immediately
before edema induction (time 0 = baseline). In the follow-
ing, such transformed data are called differential paw vol-
ume data.
Finally, one non-treated rat was repeatedly tested
throughout experiment B, to estimate the reproducibility
of the measurement instrument.
Statistical analysis
Sample size was estimated considering the two-tailed Stu-
dent t test for independent groups performed to test effi-
cacy. Specifically, we based our calculation on the
following values for the different parameters: (i) standard
deviation of paw volume increase homogeneous among
groups σ = 0.10 (based on control group data from previ-
ous works); (ii) the smallest difference in paw volume
increase between treatment and saline, worth detecting
from a biological/clinical point of view, ∆ = 0.1275 (i.e. ∆
= 1.255σ, corresponding to the half-width of the 80% ref-
erence interval of control animals); (iii) Type I error prob-
ability α = 0.007 (corresponding to an experimentwise
probability αE = 0.05 when considering the correction for
seven comparisons); (iv) power 1-β = 0.80. The resulting
sample size per group was n = 18.
The following statistical analyses were performed on col-
lected data. Differential paw volume data were checked
for normality, using the Shapiro-Wilks test. At all times
data respected the normality assumption. Moreover, the
Levene test, performed to assess the homogeneity of vari-
ance between groups, did not show any significant differ-
ence. Therefore, the use of parametric test for the
assessment of treatment effect was justified, as expected.
A mixed model analysis of variance (ANOVA) was then
performed on differential paw volume data. When analyz-
ing the repeated measures, the Huynh-Feldt correction
was used to take into account possible violation of the
sphericity assumption. We preferred this correction to the
more conservative Greenhouse-Geisser correction,
because in our opinion Type II errors would have been
more important than Type I errors in this particular study.
Multiple comparisons were performed between treat-
ments within each time by Tukey HSD test. Student t test
for independent groups was also performed to compare
treatments within each time, in order to verify if correc-
tion for multiple comparisons (included in Tukey test)
could have concealed possibly interesting effects. All sta-
tistical analyses were planned a priori, with the exception
of multiple comparisons, performed on a post-hoc basis.
For all analyses, the BMDP statistical package was used
[20].
Results
The analysis of rat weight increase from arrival to the day
of testing showed a general well being of experimental
animals, similar among treatment groups (data not
shown).
Experiment A
The experiment was replicated three times. For each repli-
cation 48 rats were used. Animals were housed in eight
cages, six animals per cage. Cage-mates received the same
treatment.
Treatment groups are described in the following. Group 1:
Arnica montana D4; Group 2: Apis mellifica D4; Group 3:
Atropa belladonna D4; Group 4: Hamamelis virginiana D4;
Group 5: Lachesis D6; Group 6: Phosphorus D6; Group 7:
sterile physiological solution of 0.9% NaCl (saline);
Group 8: indomethacin i.m. (administered 30 minutes
before edema induction).
Tables 2, 3, 4, 5 show the overall mean values (± SD) for
each remedy. The global means by treatment group were
compared using parametric ANOVA, followed by Tukey
HSD test (not shown) and Student t test for independent
groups. When treatments are significantly different from
saline at t test (p < 0.05), the results are printed in bold.
ANOVA results are reported at the foot of tables. For all
combinations of edema model and administration route,
we observed significant main effects of treatment and time
and significant interaction treatment × time. This was
expected, due to the presence of Indomethacin (standard
treatment), which always led to a significant inhibition of
inflammation in all the experimental conditions (range of
reduction from 14% to 40%).
Tables 2 and 3 respectively show the activity of the com-
pounds administered orally or by sub plantar injection on
paw volume during carrageenan-induced edema. All the
orally administered homeopathic remedies had an inhib-

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itory effect above all one hour after edema induction, par-
ticularly Apis, Lachesis and Phosphorus (Table 2). When
administered by means of sub plantar injections, the
effect of the same homeopathic remedies was significant
only in the case of Apis, after 1 and 7 hours (Table 3).
In the blood-induced edema model of inflammation
none of the orally administered remedies showed a signif-
icant effect when compared to saline solution (Table 4).
The homeopathic remedies administered by sub plantar
injections (Table 5) led to a slight inhibition of blood-
induced edema, particularly 1 hour after the administra-
tion of Arnica, Apis, Hamamelis and Phosphorus. None
showed any significant inhibitory effect after 2 hours;
Arnica and Apis induced a significant inhibition after 3
and 5 hours, Atropa and Phosphorus after 3 hours and
Hamamelis after 5 hours.
The results of Student t test are confirmed also by the
results of Tukey test (not shown).
Experiment B
On the basis of the results of Experiment A, in phase B we
chose to replicate the carrageenan edema model in rats
treated orally with Apis, Lachesis, Phosphorus. The experi-
ment was replicated three times using 48 rats for each rep-
lication. Cagemates received different treatments;
therefore, no confounding effect of cage could interfere in
the assessment of treatment effect.
Treatment groups are described in the following. Group 1:
Apis mellifica D4; Group 2: Apis mellifica D30; Group 3:
Lachesis D6; Group 4: Lachesis D30; Group 5: Phosphorus
D6; Group 6: Phosphorus D30; Group 7: sterile physiolog-
ical solution of 0.9% NaCl (saline); Group 8: indometh-
Table 3: Experiment A: Carrageenan edema and administration by sub plantar injection
Drug Paw volume increase over time (ml ± SD) and effect (% of negative control)
1 hr 3 hr 5 hr 7 hr
Saline 0.63 ± 0.09 0.92 ± 0.14 0.84 ± 0.13 0.81 ± 0.14
Arnica D4 0.59 ± 0.15 -7 0.90 ± 0.14 -2 0.86 ± 0.15 3 0.74 ± 0.15 -8
Apis D4 0.57 ± 0.08 -10 0.83 ± 0.14 -10 0.80 ± 0.13 -5 0.67 ± 0.12 -17
Atropa D4 0.61 ± 0.09 -4 0.96 ± 0.09 4 0.81 ± 0.10 -3 0.74 ± 0.15 -9
Hamamelis D4 0.62 ± 0.13 -3 0.95 ± 0.15 3 0.87 ± 0.17 5 0.69 ± 0.12 -15
Lachesis D6 0.64 ± 0.16 1 0.86 ± 0.22 -7 0.85 ± 0.20 2 0.81 ± 0.12 0
Phosphorus D6 0.59 ± 0.09 -8 0.94 ± 0.13 2 0.88 ± 0.16 6 0.74 ± 0.13 -9
Indomethacin i.m. 0.54 ± 0.12 -14 0.69 ± 0.12 -25 0.63 ± 0.11 -25 0.49 ± 0.05 -40
ANOVA results. Treatment: F(7,86) = 8.55, p < 0.0001; Time: F(3,258) = 221.19, p < 0.0001; Treatment × time: F(21,258) = 3.18, p < 0.0001.
Bold characters denote significant comparisons (by Student t test) vs. Saline group corresponding for time since edema induction.
Table 2: Experiment A: Carrageenan edema and oral administration
Drug Paw volume increase over time (ml ± SD) and effect (% of negative control)
1 hr 3 hr 5 hr 7 hr
Saline 0.57 ± 0.14 0.98 ± 0.13 0.93 ± 0.14 0.79 ± 0.14
Arnica D4 0.46 ± 0.12 -18 0.98 ± 0.14 0 0.85 ± 0.12 -8 0.72 ± 0.11 -9
Apis D4 0.42 ± 0.12 -26 0.90 ± 0.15 -8 0.77 ± 0.14 -17 0.65 ± 0.15 -18
Atropa D4 0.44 ± 0.09 -22 0.94 ± 0.16 -4 0.80 ± 0.18 -14 0.73 ± 0.17 -7
Hamamelis D4 0.49 ± 0.11 -14 0.88 ± 0.14 -10 0.78 ± 0.17 -16 0.68 ± 0.14 -14
Lachesis D6 0.41 ± 0.10 -28 0.87 ± 0.18 -11 0.81 ± 0.17 -12 0.62 ± 0.18 -21
Phosphorus D6 0.41 ± 0.13 -28 0.86 ± 0.14 -12 0.78 ± 0.13 -16 0.65 ± 0.11 -18
Indomethacin i.m. 0.38 ± 0.14 -34 0.63 ± 0.18 -36 0.59 ± 0.18 -36 0.49 ± 0.18 -38
ANOVA results. Treatment: F(7,136) = 8.38, p < 0.0001; Time: F(3,408) = 674.23, p < 0.0001; Treatment × time: F(21,408) = 3.65, p < 0.0001.
Bold characters denote significant comparisons (by Student t test) vs. Saline group corresponding for time since edema induction.

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acin i.m. (administered 30 minutes before edema
induction).
Differential paw volume data in the various subgroups are
presented as mean ± SD (Table 6). The global means by
treatment groups were compared using Student t test for
independent groups. When significantly different from
saline at t test (p < 0.05), the results are printed in bold.
ANOVA results are reported at the foot of tables. Also in
Experiment B we observed significant main effects of treat-
ment and time and significant interaction treatment ×
time. Specifically, when compared to saline, indometh-
acin showed a significantly lower increase in paw volume,
while no homeopathic treatment at any dosage gave sig-
nificant results. When examining separate replications,
significant differences between saline and homeopathic
treatments (with homeopathic treatments performing
worse than saline) were rare and sparse, mainly concen-
trated at 5 hours from edema induction. Clear-cut effect of
dilutions was never observed.
The results of Student t test are confirmed also by the
results of Tukey test (not shown).
Finally, nine measures of paw volume were collected on
one non-treated rat (arrival weight 150 g, weight at the
day of testing 200 g) to estimate the reproducibility of the
measurement instrument. The measurements ranged
from 1.14 to 1.40, with a mean of 1.25 and a SD of 0.08.
The coefficient of variation was therefore CV = 6.09%.
Discussion
Relatively few pre-clinical studies have been carried out in
toxicological research in order to verify the effects of
Table 5: Experiment A: Blood edema and administration by sub plantar injection
Drug Paw volume increase over time (ml ± SD) and effect (% of negative control)
1 hr 2 hr 3 hr 5 hr
Saline 0.80 ± 0.08 0.73 ± 0.09 0.69 ± 0.08 0.52 ± 0.07
Arnica D4 0.65 ± 0.09 -19 0.68 ± 0.11 -7 0.60 ± 0.08 -12 0.47 ± 0.07 -9
Apis D4 0.69 ± 0.09 -14 0.69 ± 0.08 -6 0.63 ± 0.08 -8 0.45 ± 0.07 -14
Atropa D4 0.73 ± 0.09 -9 0.70 ± 0.09 -4 0.63 ± 0.09 -8 0.48 ± 0.08 -9
Hamamelis D4 0.67 ± 0.13 -16 0.70 ± 0.13 -5 0.64 ± 0.09 -7 0.45 ± 0.09 -14
Lachesis D6 0.77 ± 0.09 -4 0.75 ± 0.11 3 0.63 ± 0.09 -8 0.48 ± 0.09 -8
Phosphorus D6 0.63 ± 0.13 -21 0.69 ± 0.16 -5 0.60 ± 0.15 -12 0.45 ± 0.15 -13
Indomethacin i.m. 0.69 ± 0.08 -14 0.62 ± 0.09 -16 0.49 ± 0.09 -28 0.38 ± 0.11 -27
ANOVA results. Treatment: F(7,134) = 3.92, p = 0.0006; Time: F(3,402) = 579.79, p < 0.0001; Treatment × time: F(21,402) = 4.54, p < 0.0001.
Bold characters denote significant comparisons (by Student t test) vs. Saline group corresponding for time since edema induction.
Table 4: Experiment A: Blood edema and oral administration
Drug Paw volume increase over time (ml ± SD) and effect (% of negative control)
1 hr 2 hr 3 hr 5 hr
Saline 0.60 ± 0.12 0.63 ± 0.11 0.55 ± 0.15 0.36 ± 0.13
Arnica D4 0.58 ± 0.08 -5 0.61 ± 0.08 -4 0.52 ± 0.11 -5 0.38 ± 0.11 7
Apis D4 0.55 ± 0.08 -8 0.66 ± 0.08 4 0.55 ± 0.15 0 0.35 ± 0.13 -1
Atropa D4 0.57 ± 0.08 -6 0.63 ± 0.11 -1 0.54 ± 0.15 -2 0.33 ± 0.11 -7
Hamamelis D4 0.57 ± 0.07 -6 0.62 ± 0.08 -2 0.50 ± 0.13 -9 0.31 ± 0.10 -12
Lachesis D6 0.55 ± 0.14 -10 0.63 ± 0.11 -1 0.50 ± 0.15 -9 0.31 ± 0.12 -13
Phosphorus D6 0.54 ± 0.08 -11 0.62 ± 0.09 -2 0.53 ± 0.12 -4 0.33 ± 0.09 -7
Indomethacin i.m. 0.51 ± 0.10 -16 0.46 ± 0.10 -27 0.36 ± 0.12 -35 0.22 ± 0.10 -39
ANOVA results. Treatment: F(7,135) = 4.40, p = 0.0002; Time: F(3,405) = 535.25, p < 0.0001; Treatment × time (F(21,405) = 2.66, p = 0.0004.
Bold characters denote significant comparisons (by Student t test) vs. Saline group corresponding for time since edema induction.

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homeopathic remedies under standardized conditions
and their results are not incontrovertible [2-17,19,21].
The present study was designed to explore the possibility
to test in a controlled way the effects of homeopathic rem-
edies on two known experimental models of acute inflam-
mation in the rat. To this aim, the study considered six
different remedies indicated by homeopathic practice for
this type of symptom, in two experimental edema models
(carrageenan- and autologous blood-induced edema),
using two treatment administration routes (sub-plantar
injection and oral administration).
On the overall the study involved more than 700 rats in
one of the largest pre-clinical study of the effects of home-
opathic remedies ever performed.
In the first series of experiments (phase A) some statisti-
cally significant effects of homeopathic remedies were
observed in two experimental conditions: oral adminis-
tration in carrageenan-induced edema and sub plantar
administration in blood-induced edema (reduction in
paw volume increase up to 28% and 21% compared to
the saline control, respectively). These effects were more
evident and statistically significant in the initial and/or
final phases of inflammation, when it is less marked and
probably easier to control. The most relevant results con-
cerned Apis, Lachesis and Phosporus in the oral treatment of
carrageenan-induced edema (with a range of edema
reduction from 11% to 28%). The anti-inflammatory
effects of the homeopathic remedies were approximately
50% less than those of the reference drug indomethacin.
When retested in phase B, where a double-blinding proce-
dure and coding of remedies was performed, the three
tested homeopathic remedies (at different dilutions) did
not show any anti-inflammatory effect. The lack of repro-
ducibility of the results in the second experiment may be
explained by the different experimental protocol used. In
particular, two experimental conditions were modified in
the second phase: the generation of allocation sequences
to the treatments and the blinding of these sequences.
Moreover, the blinding process could have altered the
storage of homeopathic remedies (glass in A, plastic in B),
and this was an additional source of difference in the pro-
tocols between experiments A and B.
Indeed, in the first experiment animals were randomly
allocated to cages and all animals hosted in the same cage
received the same treatment. Although it is unlikely that a
"cage-effect" has occurred during the first experiment, in
the second one, animals were randomly distributed in dif-
ferent cages and in each cage animals received the differ-
ent treatments at random. It is conceivable, at least in
theory, that some unknown "cross-effect" among animals
in the same cage, treated with different remedies, could
have taken place, thus reducing the (already low) net dif-
ference between verum and placebo. It is important to
underline that the activity of indomethacin was repro-
duced in all phases of the experiment, suggesting that if
some cross-contamination occurred, this would have
affected only saline-treated and homeopathy-treated rats
reducing all responses and decreasing a possible (small)
effect of homeopathic drugs.
Experiment B differs from A also by inclusion of higher
potencies (D30), which were hypothesized to "radiate"
through sealed ampoules [22]. This elusive effect could
leave open the possibility of some cross-contamination
during some stages of the experimental process that we
have not considered in the protocol.
Furthermore, it is important to consider the possibility of
an (unconscious) effect of the researchers, due to the
Table 6: Experiment B: Carageenan edema and oral administration
Drug Paw volume increase over time (ml ± SD) and effect (% of negative control)
1 hr 3 hr 5 hr 7 hr
Saline 0.39 ± 0.17 0.77 ± 0.16 0.63 ± 0.18 0.54 ± 0.16
Apis D4 0.37 ± 0.11 -7 0.81 ± 0.11 +6 0.70 ± 0.20 +12 0.60 ± 0.15 +11
Apis D30 0.43 ± 0.11 +8 0.82 ± 0.11 +7 0.73 ± 0.17 +16 0.59 ± 0.13 +10
Lachesis D6 0.40 ± 0.12 +1 0.79 ± 0.19 +3 0.71 ± 0.18 +14 0.58 ± 0.17 +7
Lachesis D30 0.40 ± 0.17 +2 0.79 ± 0.19 +3 0.75 ± 0.19 +19 0.59 ± 0.21 +10
Phosphorus D6 0.40 ± 0.15 +1 0.80 ± 0.18 +4 0.70 ± 0.16 +11 0.59 ± 0.20 +10
Phosphorus D30 0.41 ± 0.16 +3 0.85 ± 0.23 +11 0.72 ± 0.21 +14 0.59 ± 0.18 +10
Indomethacin i.m. 0.30 ± 0.14 -24 0.48 ± 0.15 -38 0.52 ± 0.10 -18 0.43 ± 0.10 -20
ANOVA results for measurements from 1 to 7 hrs since edema induction. Treatment: F(7,14) = 4.23, p = 0.0105; Time: (F(3,6) = 26.91, p = 0.0007;
Treatment × time (different profiles over time between treatments): F(21,42) = 2.07, p = 0.1010; Replication × time (different profiles over time
between replications): F(6,45) = 8.61, p < 0.0001; Replication × treatment × time (different profiles over time between replications and treatments):
F(42,315) = 1.65, p = 0.0110.
Bold characters denote significant comparisons (by Student t test) vs. Saline group corresponding for time since edema induction.

9. BMC Complementary and Alternative Medicine 2007, 7:1 http://www.biomedcentral.com/1472-6882/7/1
Page 9 of 10
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absence of blinding of treatment allocation in the first
phase. This may be the case if the induction of edema, the
administration of treatments or the collection of the
response variable were performed in different ways for
animals treated with verum, with placebo or with the
active reference drug. This confounding effect is rarely
controlled in conventional animal research (thus consti-
tuting a possible weak point of this discipline), while it is
appropriately taken into account almost always in clinical
research. However, even if it is difficult to conceive how
this confounding effect could have acted in our experi-
mentation, it cannot be totally excluded [23,24]. The fact
that the effects of the homeopathic dilutions studied in
pre-clinical tests carried out by different research groups,
when observed, are often small and difficult to reproduce
[11], emphasizes the relevance of the experimental condi-
tions in which significant effects can be observed.
The experimental models we used to evaluate anti-inflam-
matory treatments have explored what is conventionally
denoted as pharmacological "activity" on one symptom
(e.g. foot swelling). While conventional anti-inflamma-
tory drugs are designed to suppress the underlying enzy-
matic mechanism of inflammation (e.g. prostaglandin
production), homeopathic treatment is supposed to regu-
late the pathological excess of inflammation because the
phenomenon by itself is seen as an expression of natural
healing dynamics (the so called Hahnemann's "life
force"). According to classical homeopathic theory, an
"anti-edema" effect could not reflect the full potential of
the homeopathic treatments of inflammatory diseases.
On the other hand, other experimental approaches and/or
different formulations showed consistent anti-inflamma-
tory effects of homeopathic remedies such as Arnica com-
positum [2,3], Apis [7] and Arnica Montana [25] using the
rat-paw edema model. So, other technical factors, such as
the composition of the medicines (e.g. single remedies
versus complex formulations), and the type of solvent
used (water, saline, water/alcohol mixtures) [26], may
explain the observed discrepancies. If a homeopathic
treatment acts by influencing the natural healing dynam-
ics of the whole treated subject by means of small doses or
highly diluted administrations, this action could be, at
least in theory, highly sensitive to even small changes in
experimental conditions [27]. Moreover, when used in
humans, a homeopathic treatment is also chosen on the
basis of the global pathophysiological characteristics of
the individual, and not only in relation to local symp-
toms.
Conclusion
In conclusion, the discrepancies observed in the two
phases of our study make it possible to draw some sugges-
tions useful for designing possible further experiments: a)
the effects, when obtained, are relatively small, thus exper-
imental conditions which may affect the response,
increasing the variability between experiment results,
should be accurately controlled; b) the discrepancies
between single-blind (measurement) and double-blind
(treatment administration and measurement) methods in
animal pharmacological research are noteworthy and sug-
gest that full blinding of procedures (drug administration,
data collection and analysis) may be a critical factor for
the results of animal experimental investigations, also in
non-homeopathic research.
Competing interests
The author(s) declare that they have no competing inter-
ests.
Authors' contributions
AC, PB, SB conceived the study, participated in its design
and carried out the experiment. FC and FMI, refined the
experimental design, provided the power calculation, per-
formed the statistical analyses and drafted the manuscript.
RR, participated in the study design, coordinated the
study and drafted the manuscript. All authors read and
approved the final manuscript.
Acknowledgements
We thank Elia Castellani for his technical help in measuring paw volumes
(even after his retirement), Angelina Valanzano for the coding of treatments
in Experiment B, Gemma Calamandrei for her useful comments on animal
experiments and Monica Bartolomei for the ultraviolet analysis of drugs.
The study was made possible by a grant from the Ministry of Health, Project
"Unconventional Therapies" (art 502, fasc 99/S).
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